The field of the invention relates generally to devices for delivering fluids, such as solutions, dispersions, suspensions, gels, pastes, or other like materials having a broad range of viscosities.
In particular, the field of the invention relates to a system for multiple dose controlled delivery of flowable materials. The system provides for unidirectional, laminar flow to increase the rate of delivery at relatively low applied pressures. At the same time the system prevents backflow and contamination of the flowable material from air and airborne pathogens or even from direct contact with microorganisms by immersion in concentrated suspensions of viruses or bacteria, to thereby maintain the sterility and integrity of a flowable material without the need for preservatives, antioxidants or other additives.
The dispensing of flowable materials in a contamination-free manner, especially over prolonged periods of time or in a repetitive manner, such as delivery of multiple doses, presents many difficulties. A major problem to be overcome concerns precise flow control and the prevention of backflow or reflux. External contaminants easily can enter a container through the backflow effect at the end of a delivery cycle.
Many fluids including viscous solutions are delivered through a collapsible or volumetrically reducible container which has a discharge port, such as a hole, nozzle, spout, or other type of opening. The contents of the container, such as a viscous paste, liquid, or other solution are delivered through the discharge port by internal pressure or by squeezing the container. Such a conventional method of dispensing a viscous material is inaccurate and fails to prevent the entry of external contaminants into the container due to a backflow or reflux effect. That is, a conventional system for delivering a fluid typically allows air to replace the fluid that is expressed. In addition, as the volume of fluid in the container is reduced through successive delivery, flow becomes inaccurate, uneven and difficult to control. Such a conventional delivery system is highly undesirable when being used to administer a flowable material which needs to be closely controlled. In addition, if the discharge port is used in a contaminated environment, the entry of air, dust, filaments, airborne pathogens or microbes, quickly can damage the integrity of the contents of the fluid.
For example, many flowable materials are highly labile. Labile substances are difficult to preserve and break down quickly due to oxidation or hydrolysis. Many medications lose their effectiveness quickly when exposed to repeated influx of air or external contaminants in the course of regular use. In addition, many medications lose their effectiveness when combined with antimicrobial agents.
Thus, what is needed is a system for delivering a labile, flowable material, such as a medication, without danger of external contamination or loss of integrity due to exposure to air, dust, filaments, airborne pathogens, or antimicrobial agents. Such an improved delivery system would enhance the effectiveness of a labile medication, such as an ophthalmic solution, and would be capable of maintaining sterility throughout many uses over long periods of time. Such an improved delivery system also would effectively maintain the integrity of a fluid throughout its period of use and would extend the fluid's use life to that of its shelf life.
It has been found that the addition of some antimicrobial agents to labile medications not only can shorten overall use life and effectiveness, but also may produce deleterious side effects on a patient, such as delaying post-surgery healing rates. Conventional approaches to dispensing a flowable medium while alleging to prevent air, airborne pathogens or microbial contaminants from degrading the integrity of the flowable medium have not demonstrated they can do so, nor prevent viruses or bacteria from entering the dispensing container through contact or immersion. Therefore, it would be advantageous to develop a system for delivery of a flowable medication without contamination, even on direct contact with viruses or bacteria. Such a system would enable the medication to be delivered free of antimicrobial agents and therefore would achieve an enhanced therapeutic effect and a substantially prolonged use life.
It also would he advantageous to provide a system for delivery of a fluid, even a highly viscous material at an improved flow rate, such that the unit dosage delivered remained constant over time.
It also would be advantageous to provide an improved system for delivering a viscous material, such as a paste, gel, or other viscous substance, in a highly controlled, constant manner, irrespective of the change in volume of the volumetrically reducible container through repeated usage.
It also would be advantageous to provide a system for delivering a highly viscous material with a constant laminar flow and a simplified unidirectional flow path which could be completely cut off after each use, preventing the entrapment of material and providing a complete seal against contamination even by air or when in direct contact with microbes.
What is also needed is a system for delivering a fluid, such that a predetermined cracking pressure is achieved. The cracking pressure advantageously could be optimized for ease of flow and ease of use. Alternatively, it would be desirable it the cracking pressure also could be made higher, such as for impeding flow for safety considerations.
The foregoing, and other disadvantages of conventional contamination-free delivery systems may be seen with reference to FIGS. 1A-1D. Referring to FIG. 1A, Gerber, U.S. Pat. No. 4,846,810 and Pardes, U.S. Pat. No. 5,092,855 disclose generally a valve or delivery system with central body core, delivery block or seat as shown. The arrows indicate the flow of a flowable material into and through the seat to its exit port. It is assumed that the container of flowable material is attached to the entrance port of the valve and flowable material passes through the valve in the path shown by the arrows. The container is not shown for the sake of simplicity. As is well understood by those skilled in the art, an enclosing sleeve (not shown) surrounds the valve body and constrains the flow of material in the direction shown by the arrows. The enclosing sleeve retains an elastomeric sheath or seal against the valve body, thereby providing a seal between the sheath and valve body. Note that this design produces generally a convoluted flow path having at least four changes of direction for the flowable material (please refer to FIG. 1A).
In accordance with FIG. 1A, each delivery system or valve operates through two sets of ports within the valve body, thus rendering the flow path unnecessarily complex and unsuitable for viscous applications. For example, viscous material may become lodged or retained between the valve body and the enclosing sheath after use of the valve, thereby creating avenues for the entry of airborne pathogens. In addition, the complex flow path constrains the optimized delivery of a viscous material. In contrast, what is needed is a contamination-free delivery system which not only prevents contamination or degradation of the flowable material, but which also accelerates the flow rate of a viscous substance at low applied pressures.
Another conventional delivery system is shown in FIG. 1B. Haviv, U.S. Pat. No. 5,080,138, discloses a valve assembly relying on a sleeve valve and consisting of multiple components. Backflow is prevented by a sheath which permits flowable material to flow out of the valve and attempts to prevent backflow into the container. This device is not suitable for highly viscous solutions which can prevent the sheath valve from returning to its closed position to block backflow or reflux. Also, such a conventional delivery system creates a complicated flow path with four changes of direction as shown by the arrows in FIG. 1B. Such a device does not provide a high rate of flow or ease of flow of a viscous material. It also fails to protect against contamination through immersion in or direct contact with suspensions of viruses or bacteria.
Another example of a conventional delivery system is shown in FIG. 1C. Debush, U.S. Pat. No. 5,305,786 attempts to prevent contamination by an expandable elastomeric sleeve tightly fitted about a valve body with entry and exit ports, as shown by the arrows. However, this solution requires additional material to manufacture the valve and produces a complex flow path, characterized by at least three changes of direction, which is not suitable for delivering a viscous material. (See FIG. 1C.)
FIG. 1D (U.S. Pat. No. 5,836,484) shows a multiple-dose dispensing cartridge for contamination-safe delivery of flowable materials. While this design has been proven effective against airborne or microbial contamination, the design forces the fluid flow path to change direction at least four times between the entry and exit of the fluid, as shown by the arrows in FIG. 1D. Each time the direction of the flow path changes, the velocity and flow rate of the flowable material are reduced. In addition, such a convoluted flow path is not suited to the delivery of large volumes of material. Additionally, a complex flow path with frequent changes of direction is not at all suited to the delivery of a viscous material. Not only would delivery of the viscous material require an inordinate amount of pressure, the closure of the valve would be slowed by numerous pockets of viscous material which could be trapped in the complex flow path. This could lead to ineffective or uneven closing of the valve and may provide an avenue of entry for air, airborne pathogens, or other microbes. In addition, any viscous material left in the complex flow path which is exposed to the air may provide a source of contamination for successive deliveries of that material.
None of the conventional dispensing devices shown generally in FIGS. 1A-1D are simple in construction and capable of delivering a flowable material ranging from low to high viscosity.
In addition, the conventional methods discussed above and as shown in FIGS. 1A-1C may not be capable of maintaining a sterile condition once the apparatus is used or opened to the atmosphere. This is particularly true of viscous solutions which may be trapped in the tortuous flow path when the flow is shut off. A viscous solution often does not permit an efficient sealing of the valve after use, and provides unconformities and pathways for microorganisms such as a virus to enter and contaminate the contents of the container.
Another problem in conventional systems for the delivery of a flowable medium is the inability to achieve a constant flow rate. As the volume of a reducible reservoir containing fluid is decreased, the flow rate of the fluid varies. In addition, the cracking pressure or the pressure at which the viscous medium flows can be affected by the amount of material in the container, the size of the container, the viscosity of the fluid, the flow path of the fluid and like factors. Conventional delivery devices have no way to maintain a constant flow rate.
What is needed is an improved method for delivering fluids of varying viscosity up to many thousands of centipoise. What is also needed is a method and apparatus for achieving an optimized cracking pressure for fluids of varying viscosity. That is, it would be advantageous to set the cracking pressure for the delivery mechanism at an optimal point for ease of activation, particularly for children and the elderly. No conventional device addresses the need for a desired activation threshold to achieve a desired cracking pressure and flow rate.
It also would be advantageous to achieve an optimized cracking pressure for a highly viscous medium, while at the same time maintaining the integrity and sterility of that medium and preventing contamination of that medium from any source, including air or through direct contact even when immersed in suspensions of microbes, such as viruses or bacteria. This advantageously would enable a labile, viscous, flowable medium, such as a medication, to be reformulated without antimicrobial agents or other additives, and to be delivered in a precise unit dose. The ability to deliver large volumes of flowable media at an optimized cracking pressure also would allow for ease of use.
With the exception of U.S. Pat. No. 5,836,484, conventional delivery systems are not scalable to permit high rates of delivery of large volumes of flowable media. Therefore, what is also needed is a delivery system which not only would maintain the sterility and integrity of the flowable medium, but at the same time enable its rate of flow and cracking pressure to be closely controlled at desired values. It also would be advantageous to provide a delivery system capable of achieving high rates of flow of a highly viscous fluid by optimizing the cracking pressure, while at the same time enabling, the flow to be cut off completely, without reflux or any contamination.
Another problem of conventional devices for delivering a flowable medium is the inability to maintain the integrity of a flowable medium and to extend its useful life to that of the shelf life. For example, conventional dispensing devices cannot maintain the carbonation of a multiple use carbonated flowable medium. There is a gradual release of carbonation each time the product is dispensed. Therefore, it also would be desirable to provide a method for dispensing a flowable medium which maintained its integrity, including, carbonation or other inherent properties, and thereby extended the useful life of the product.